Night-time screen-based media device use and adolescents’ sleep and health-related quality of life.

Objective: The present study investigates the relationship between night-time screen-based media devices (SBMD) use, which refers to use within one hour before sleep, in both light and dark rooms, and sleep outcomes and health-related quality of life (HRQoL) among 11 to 12-year-olds.\ud Methods: We analysed baselined data from a large cohort of 6,616 adolescents from schools in and around London, United Kingdom, participating in the Study of Cognition Adolescents and Mobile Phone (SCAMP). Adolescents self-reported their use of any SBMD (mobile phone, tablet, laptop, television etc.). Sleep variables were derived from self-reported weekday and/or weekend bedtime, sleep onset latency (SOL) and wake time. Sleep quality was assessed using four standardised dimensions from the Swiss Health Survey. HRQoL was estimated using the KIDSCREEN-10 questionnaire. \ud Results \ud Over two-thirds (71.5%) of adolescents reported using at least one SBMD at night-time, and about a third (32.2%) reported using mobile phones at night-time in darkness. Night-time mobile phone and television use was associated with higher odds of insufficient sleep duration on weekdays (Odds Ratio, OR= 1.82, 95% Confidence Interval, CI [1.59, 2.07] and OR=1.40, 95% CI [1.23, 1.60], respectively). Adolescents who used mobile phones in a room with light were more likely to have insufficient sleep (OR=1.32, 95% CI [1.10, 1.60]) and later sleep midpoint (OR=1.64, 95% CI [1.37, 1.95]) on weekends compared to non-users. The magnitude of these associations was even stronger for those who used mobile phones in darkness for insufficient sleep duration on weekdays (OR=2.13, 95% CI [1.79, 2.54]) and for later sleep midpoint on weekdays (OR=3.88, 95% CI [3.25, 4.62]) compared to non-users. Night-time use of mobile phones in light was not associated with HRQoL but use in darkness was associated with a lower KIDSCREEN-10 score (β= -1.19, 95% CI [-1.83, -0.56]) compared to no use. \ud Conclusions: We found consistent associations between night-time SBMD use and poor sleep outcomes and worse HRQoL in adolescents. The magnitude of these associations was stronger when SBMD use occurred in a dark room versus a lit room